Touch screens for electronic devices such as mobile phones or tablet PCs are made of material with low hardness (such as glass), thus which are easily worn and torn by hard material such as small gravels or keys during the daily use, to causes some scratches on the touch screens or even makes the touch screens invalidate. Furthermore, grease and fingerprints on the user's skin are easily remained on the surface of the touch screen, which reduces the visual clarity and the screen effect.
Nowadays, a technique by coating a diamond-like carbon (DLC) film on the touch screen to improve the hardness, scratch and abrasion resistance, and hydrophobicity and oleophobicity has been developed.
For example, U.S. Pat. No. 5,637,353 discloses a method for forming a DLC film on the glass substrate. The DLC film made by Chemical Vapor Deposition (CVD) has a good wear resistance, without a good hydrophobic performance and a high light transmittance due to the thick DLC however. U.S. Pat. No. 6,280,834 discloses a method for forming a DLC film on the glass substrate by Ion Beam Deposition and Chemical Vapor Deposition (IBD-CVD). In this method, C2H2 is used as the ion source, and the DLC film made by IBD includes a high quantity hydrogen (H) and less tetrahedral amorphous carbon (ta-C) structure with SP3 bond that has high hardness, such that the DLC film has lower hardness with 10˜30 GPa, and thus the wear resistance is bad. Chinese publication patent application CN 102529214A discloses a method for making a DLC film on a substrate (such as glass, ceramics, and the like) by CVD. Further, a fluorine (F) layer is doped on the surface of the DLC film so as to obtain good hydrophobicity and oleophobicity. However, the DLC made by this method is doped with H and forms H-C bonds, thus tetrahedral amorphous carbon (ta-C) structures with hard SP3 bond are less, which brings low hardness of 5 GPa around and bad wear resistance therefore. An option to improve the wear resistance is increasing the thickness of the DLC film, which will reduce the light transmittance however.
Thus it's difficult for the conventional DLC films made by the conventional methods to satisfy the requirements of good bonding force among films, high hardness, good wear resistance, good hydrophobicity and high light transmittance. Especially the DLC film is doped with H due to the CVD method, therefore it is difficult to improve the hardness and scratch and abrasion resistance.
Therefore there is a need for an improved article coated with DLC and an improved manufacturing method thereof to overcome the above-mentioned drawbacks.